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Transformer
About A transformer is a device that transfers electrical energy from one electrical network to another through inductive coupling conductors — the transformer's coils or "windings". Except for Transformer Cores transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the first or "primary" winding creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic field's electromagnetic induction a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction. If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will flow from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary to the number of turns in the primary as follows: : \frac{V_{S}}{V_{P}} = \frac{N_{S}}{N_{P}} By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP. Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical. See power supply for final components. Lastly, an ideal transformer, the magnetizing current would rise to approximately twice its normal peak value as well, generating the necessary mmf to create this higher-than-normal flux by a substantial surge of current through the primary winding called inrush current. Transformersound Direction of force The right-hand rule: With the thumb of the right hand pointing in the direction of the conventional current or moving positive charge and the fingers pointing in the direction of the magnetic field the force on the current will be in a direction out of the palm. The direction of the force is reversed for a negative charge. The direction of force on a positive charge or a current is determined by the right-hand rule. See the figure on the right. Using the right hand and pointing the thumb in the direction of the moving positive charge or positive current and the fingers in the direction of the magnetic field the resulting force on the charge will point outwards from the palm. The force on a negative charged particle is in the opposite direction. If both the speed and the charge are reversed then the direction of the force remains the same. For that reason a magnetic field measurement (by itself) cannot distinguish whether there is a positive charge moving to the right or a negative charge moving to the left. (Both of these will produce the same current.) On the other hand, a magnetic field combined with an electric field can distinguish between these, see Hall effect below. An alternative, similar trick to the right hand rule is Fleming's left hand rule. Reference Links See also http://www.youtube.com/watch?v=QqaxkGcEzeI How to check a Transformer Video * * Category:Electronics Category:CBET Study Info Category:Components